Conventionally, an electric motor control apparatus to be used in a semiconductor manufacturing apparatus, a positioning apparatus such as a machine tool or an industrial robot is constituted as shown in FIG. 15.
FIG. 15 is a view showing the whole structure of the electric motor control apparatus according to the conventional art, and description will be given by taking a positioning apparatus as an example.
In the drawing, 2 denotes a servo control device, 3 denotes a rotation detector, 4 denotes an electric motor, 5 denotes a transmitting mechanism, 6 denotes a movable section, and 7 denotes a non-movable section. In this case, the transmitting mechanism 5 and the movable section 6 which constitute a load machine indicate a ball screw and a table respectively, and the non-movable section 7 indicates a base. Moreover, 8 denotes an operation command signal, 9 denotes a rotation detector signal, and 10 denotes a control signal. Furthermore, 17 denotes a signal generator and 18 denotes an FFT analyzer, and both of them grasp the frequency characteristic of the load machine and are used for devices required for the servo regulation of the control apparatus.
In such an electric motor control apparatus, first of all, the signal generator 17 outputs the operation command signal 8 and the operation command signal 8 is then sent to the servo control device 2. Next, the operation command signal 8 input to the servo control device 2 is sent as the control signal 10 to the electric motor 4, and operates the movable section 6 through the transmitting mechanism 5 by the rotating force of the electric motor 4. Thereafter, the rotation detector 3 sends the rotation detector signal 9 of the electric motor 4 to the FFT analyzer 18 through the servo control device 2. Subsequently, the FFT analyzer 18 carries out a fast Fourier calculation by using the operation command signal 8 received from the signal generator 17 and the rotation detector signal 9 received from the servo control device 2 and then calculates a frequency characteristic, and decides the characteristic of the load machine from the result of the calculation.
In the conventional art, however, the expensive FFT analyzer 18 is required for measuring the frequency characteristic of the load machine. Therefore, there is a problem in that the cost of equipment is increased. In order to decide the frequency characteristic measured by the FFT analyzer 18, moreover, an operator requires advanced expertise and experiences for reading a resonance frequency, an anti-resonance frequency and an attenuation. For this reason, there is a problem in that time and labor are taken.
When the servo regulation of the electric motor control apparatus is to be carried out, therefore, there has been required an apparatus capable of automatically reading an anti-resonance frequency, a resonance frequency and an attenuation from a frequency characteristic obtained by an actual measurement and modeling the characteristic of a machine which can be utilized for the simulation and the servo regulation of the control apparatus.
The invention has been made in order to solve the problems and has an object to provide a machine model estimating device of an electric motor control apparatus which can estimate a machine model to be easily utilized for a simulation and a servo regulation by automatically reading an anti-resonance frequency, a resonance frequency and an attenuation from a frequency characteristic measured value without using an expensive measuring apparatus even if an operator has neither advanced expertise nor experiences, and is inexpensive.